PS v5 compatibility fix

Several internal functions had parameters named $IV (for Initialization Vector), which conflicts with the alias for the new -InformationVariable common parameter.

Fixes #13

Updated build script

So it'll stop crapping out trying to remove / overwrite Security.Cryptography.dll if I have the module imported already.  DLL is now signed right in the source control repo, and the build script no longer overwrites that signature, so its hash doesn't change and the build script won't try to copy it.

Automatic detection of decryption certificates

The Certificate parameter of Unprotect-Data is no longer mandatory.  If a matching certificate is found in the Personal store of either the user or the machine (and the private key is accessible in either location), then that cert will automatically be used to decrypt.

Also fixed a bug that was producing KeyData objects that were hashtables instead of PSCustomObjects when encrypting data with an ECDH certificate.  (All of the code still works either way, but it was inconsistent.)

Manifest update

Just realized 4.1.0 was never actually released; bumped the version number back down and included the old release notes as well.

Updated release notes

Merge pull request #10 from dlwyatt/v3.0.1

V3.0.1

Merge pull request #9 from dlwyatt/v3

Removed deprecated CertificateThumbprint parameters

Updated build script to exclude new test file.

Updated version to 2.0

Latest update is a breaking change, so version number is now bumped to 2.0

Updated module version number.